As it is known, the term “power-supply controller” means a device converting and regulating the available power provided by a source into the power required by a load having features which are incompatible with the source features. Such a device is also called power converter.
The well known power-supply DC-DC regulators of the interleaved type usually comprise a controller and N modules or phases, in turn comprising a High Side switch and a Low Side switch realized by means of power transistors. It is assumed that a current I is required at the output, the current I being equally split between the N modules.
In particular, as shown in FIG. 1, each module or phase 10 comprises a transistor MH acting as a High Side switch connected in series to a transistor ML acting as a Low Side switch between a first and a second voltage reference, in particular an input voltage Vin and a ground GND.
The module 10 also comprises an inductor L and an output capacitor Cout coupled between an intermediate node X between the transistors MH and ML and the ground GND.
An output voltage value Vout of the module 10 is across the capacitor Cout.
At present, the market of the controllers being used for CPUs (Computing Processing Unit) is orienting towards consumer applicative solutions whereon the cost and the price erosion have generated a high push towards the cheapest possible solutions to the limits of the processor requirements. On the other hand, the speed at which this market develops imposes a compromise between highly integrated solutions (thus cheaper) and flexible solutions that are capable of meeting very short production requirements.
In particular, some solutions prevailed wherein the controller only provides for the control processing and to the power management, while the real power portion (comprising driving circuits—driver—of the Low Side and High Side transistors and more recently also PowerMOS Low Side transistors) has been confined outside the controller.
This choice mainly derives from the difficulty in simultaneously dealing in a precise way with so-called signal and power components.
Controllers for which the hard task of the power and signal integration has been attempted have used as reading method the reading of a signal across the parasitic resistance of the inductor L. In this case, however, reading occurs on a much smaller signal (about ten times smaller) and reading circuits must thus be designed, in a more precise way, and thus they are more expensive in terms of area. These circuits have however unsolved problems linked to the noise generated by the drivers themselves.
Multiphase controllers capable of reading both on the Low Side transistor and on the inductor L are also known, such as for example the L6711 controller marketed by STMicroelectronics, S.r.I. (the Assignee). In particular, this controller has drivers integrated on the same semiconductor substrate as the reading circuits of the controller modules.
This controller has an interleaving DC-DC configuration, used as a cheap and effective solution.
The so-called interleaving configuration typically requires a convenient clock circuit closing the high-side switches of the modules composing the controller with a phase shift being equal to the switching period divided by the number N of modules.
It should be pointed out that, by applying a known voltage mode control to a controller with an interleaving topology an uncontrolled distribution of the currents flowing in the inductances of the parallel modules may be obtained. It is thus often necessary, for a correct controller operation, that the total load current is equally distributed between the different modules, i.e., that each module carries a current corresponding to the current required at the output divided by N. In this case it is the “current sharing” control technique.
This controller uses, as a sense element of the single phases composing it, the parasitic resistance Rdson of the Low Side transistors. In that case, the signal corresponding to Rdson•I (where I is the phase current and Rdson a turn-on resistance of the Low Side transistor ML) is available only when the Low Side transistor ML is actually turned on by the controller. The reading circuit of the voltage Rdson•I must thus be activated only in this situation.
It is also known that an estimate of the phase current obtained by sampling the signal Rdson•I allows a controller to be implemented, which has excellent response features to the CPU load transients, and it also allows a signal to be obtained, which is useful for the so-called “current sharing” control and for protecting the controller from shortcircuits.
These controllers are thus equipped with a TRACK&HOLD device. In particular, during the sampling step the signal Rdson•I is detected (TRACK) and the reading circuit holds (HOLD) the last information being acquired.
In the case of a controller having at least three phases and drivers being integrated on the same substrate comprising the reading circuits, the reading of the signal Rdson•I is affected by the noise caused by the switching of the power transistors in the drivers which control the phases.
In that case, the track information is thus irreparably damaged by the noise produced by the switching of the external power transistors of the drivers integrated on the same silicon wherein the current reading circuits are also integrated (through the common substrate).
In order to solve the problem, insulation techniques of the drivers with respect to the analog section comprising the current-sense circuits are presently used, such as the die-to-die bonding, SOI substrates, etc. However these techniques are complex and expensive.
Therefore, a need has arisen for a method for generating a reading signal of a sense element in a phase of a multiphase controller having such structural and functional features as to allow the single step currents to be correctly read both on the low side transistors and on the inductors even with drivers being integrated on the same substrate as the current-sense circuits, and thus comprising power transistors. The noise produced by the switching of the power transistors would be eliminated through such a method, and many of the limits and/or drawbacks still affecting the controllers realized according to the prior art would be overcome.